Conventional mass flowmeters include thermal mass flowmeters which use a flow sensor. This flow sensor has a diaphragm and a sensor chip having a space immediately below the diaphragm such that two sensor resistors and a heater resistor are formed on the diaphragm. The two sensor resistors and the heater resistor are disposed in order of the sensor resistor, the heater resistor, and the sensor resistor in the flowing direction of a fluid (e.g., see Patent Literature 1).
Sensor resistors have a resistance that varies with a temperature change. In order to reduce the influence of the heat capacity of the diaphragm to the sensor resistors, the diaphragm is formed as thin as possible. The space immediately below the diaphragm is provided to reduce thermal influence from the sensor chip to the sensor resistors.
The conventional mass flowmeter uses the sensor resistors to detect a temperature change of a fluid due to a change in the mass flow rate of the fluid.